The old 'Part V' clause obliged home builders to set aside up to 20pc of all units for social or affordable housing. These homes were bought by local authorities.

Last year this requirement was reduced to 10pc for social housing - and the affordable clause was removed - despite growing pressure on prices.

But the Construction Federation of Ireland (CIF) said builders could not cope with providing a higher rate of affordable homes.

Hubert Fitzpatrick, director of housing, planning and development with the CIF, insisted that even the current 10pc was difficult for many developers to manage.

"In an environment when, in many cases, the cost of building is higher than market value of the product, the restoration of the 20pc level to Part V simply is not sustainable and can't be borne by the industry.

"We certainly welcome the change to 10pc and we would be of the view that even 10pc is difficult to manage in many parts of the country," he said.

He was responding to Ned Brennan, CEO of the Respond Housing Association, who said the level must be restored if there was to be an adequate level of social housing.

"If 12,000 units were delivered last year and half of those, 6,000, were once-off houses, that left probably 6,000 that come under the remit of Part V. So that would deliver 600 houses in the whole economy. Six hundred houses at a time where there is a need for a minimum of about 6,000 social houses per year. So the delivery of the Part V mechanism is very significant," he said.

Mr Brennan also said the Housing Strategy 2020 was "totally unachievable" based on current output. He called for the establishment of a housing authority and the delivery of fast-track planning for social housing for a five-year period.

The pair were speaking at the sixth Annual International Construction Management Day at Galway-Mayo IT.

The conference also heard from Marian Finnegan, chief economist at Sherry FitzGerald Group. She criticised Central Bank rules on mortgage lending, warning the immediate reaction to the changes had been "quite damaging".

She said people's ability to buy property had been "severely hindered".

Councillors reject plan for Travellers

A report on the future of Traveller accommodation has been rejected by councillors in Galway, who criticised officials for a lack of consultation on the matter.

The report on the 2014-2018 Traveller Accommodation Plan provided for the delivery of traveller accommodation including standard housing, group housing schemes and halting sites.

City councillors rejected the plan, claiming there had been a lack of consultation with the relevant stakeholders. They requested that consultation take place on an electoral area by electoral area basis.

Negotiations are continuing with up to 10 traveller families, including 15 children who have been moved four times in recent months. They are currently based at the city's Ballyloughane Beach.